Project Abstract The overarching aims of this Center are to help advance the clinical, research, and educational goals of the ChiLDReN grant with a particular emphasis on engaging cutting-edge genome studies as a basis for discovery, innovation, and improvements in outcomes and care. As such, the aims of this application are not only to provide comprehensive research opportunities for all children who fit enrollment criteria for ChiLDReN throughout the Southeastern US, but to embark upon 1 pilot clinical trial and 2 genomically-centered Translational Aims: Aim 1: Continued robust Clinical Center participation in all aspects of ChiLDReN. This site is one of the largest enrollers in all ChiLDReN studies, the only ChiLDReN site in the SouthEast, and we have the infrastructure to continue, and likely expand our ability to successfully enroll and retain participants. Aim 2: Open label safety and tolerability trial of an ASBT inhibitor in biliary atresia (BA). There are no treatments that improve the outcome of Kasai Portoenterostomy (KPE) in children with BA. A central pathophysiological exacerbant of liver disease in BA is intrahepatic retention of bile acids. We will build upon pre-clinical and exisiting safety data to perform a Phase 2a open label pilot trial of use of an ASBT inhibitor (ASBTi) in 20 BA participants for 18 months, starting soon after KPE. This reduction in hepatic bile acid accumulation is expected to improve the response to KPE, and inform a followup Phase 2b randomized placebo-controlled study in the ChiLDReN network. Aim 3: Discovery and validation of genetic causes of BASM. A major translational component of the recent cycle of ChiLDReN support has been a focus upon utilization of modern genomic technologies. Specifically, we have begun to test the paradigm-changing hypothesis that there is a genetic etiology for BA with splenic malformation syndrome (BASM), that subgroup of patients that present with developmental laterality defects. A first candidate gene has been identified, but additional genetic and lab-based validations are needed. A coordinated approach with cell culture and development of up to 5 CRISPR-based flox'd mouse lines will accelerate first-step discoveries and provide a reagent base for the research community at large. Aim 4: Discovery of genomic and environmental (exposomic) contributors to pediatric Primary Sclerosing Cholangitis (PSC). A recently funded multi- center study of Adult PSC (RC2 DK118619; Lazaridis PI) involves integrating clinical data with genomic, transcriptomic, metabolomic, microbial, and environmental (exposome) analyses to identify causes and contributors to the progression of PSC. We will synergize the existing analytics of the RC2 (including the Emory-based HERCULES omics center) paired with the biospecimen and clinical data collected in the newly- developed pediatric PSC observational study.